Multiple pole vacuum switch



y 1959 L. 8. sTEwARD ETAL 2,886,671

- MULTIPLE POLE VACUUM SWITCH Filed Sept. 27, 1956 INVENTOPS LEW/8 B.STEWAPD JACK 8. HAWK/NS BY their ATTORNEY United States Patent MULTIPLEPOLE VACUUM SWITCH Lewis B. Steward, San Jose, and Jack S. Hawkins,Campbell, 'Calif., assignors to Jennings Radio Manufacturinggorporation, San Jose, Calif., a corporation of Caliorma ApplicationSeptember 27, 1956, Serial No. 612,442

8 Claims. (Cl. 200-444) Our invention relates to vacuum switches,particularly of the multiple pole type.

One of the principal objects of our invention is the provision of amultiple pole vacuum switch having a substantially perfect reliabilitywithin the range of capacity, power and operative life for which it isdesigned.

Other objects of our invention include the provision of a multiple polevacuum switch capable of withstanding without impairment in operation,the most violent acceleration and shock and high temperature; havingminimum contact resistance; having a self-contained actuator with powerrequirements in the low ranges; and characterized by extremely lowinductance; miniature size; extremely rugged construction, andadaptability for mass production at low cost.

There are many other objects of our invention which will be brought outin the following description. We do not limit ourselves to the showingmade by said description and the drawings, since we may use variantforms of the invention within the scope of the appended claims.

The development of guided missiles has required a switch having thecharacteristics above referred to. Most of these newly designed piecesof equipment require a vacuum switch of multiple pole type to handle amultiplicity of operations. Generally, the voltages are low, and thecurrents also are in low range. However, to insure absolutely reliableas well as efiicient operation, we have designed our switch for highcurrent carrying capacity as compared to voltage breakdown. In theswitch illustrated, we assume these voltages never to exceed 1000 andthe test voltages on the pumps never to exceed 1500.

structurally, the vacuumized envelope of our switch is formed bybrazingtogether an assembly of annular pieces or rings of metallizedceramic material, alternating with thin, flat, conductive feed andcontact rings, a common feed ring lying between two contact rings; andthus controlling two circuits. In the drawings, Fig. 1 shows four commonfeed rings and eight separate controlled circuits.

The lateral cylindrical wall thus formed by the rings is closed at itsopposite ends with metallic plate structures; one of which provides amounting for a metallic tubulation, and the other of which provides amounting for the operator mechanism, part of which is within theenvelope and part outside of it.

An important feature of our invention lies in our assembly and sealingof components, the easily accessible interior surfaces of which havepreviously been cleaned, so that the closed assembly does not requirethe difiicult washing to remove oxides and contamination which hasheretofore been necessary in the manufacture of vacuumized envelopeshousing electrical devices.

By our method of construction, the extremely simple component parts lendthemselves to rapid clean assembly and brazing together to form anhermetically tight envelope, ready for evacuation and final bake-outheating.

2,886,671 Patented May 12, 1959 Referring now to the drawings which arethree times actual size:

Fig. 1 is a vertical half sectional view of our multiple switch, theplane of section being indicated by the line 1-1 of Fig. 2.

Fig. 2 is a horizontal sectional view of our switch, the plane ofsection being indicated by the line 2-2 of Fig. 1.

Fig. 3 is an elevation of the stem and attached arma ture, theinterposed cap being in vertical section.

Fig. 4 is a perspective view of one of the movable contact shoes.

Fig. 5 is a plan view of one of the feed or contact rings.

In the main body of our switch we use ceramic rings 2 which have beenmetallized on both flat faces, alternated with molybdenum rings 3 untilthe required length of the cylindrical assembly is attained. This isdetermined by the number of circuits the switch is to control.

The rings 3 as shown in Fig. 5, are all the same shape, and whiledisposed alternately with the ceramic rings 2, are in themselvesarranged in groups of three, a feed ring 3f, Fig. 1, with a contact ring30 on each side of it. Each of the rings 3 is provided with an outwardlyextending lug or tab 4, serving as an outside terminal or lead forconnecting the ring into a circuit. In the assembly shown in Figs. 1 and2, these lugs are spaced around the envelope apart to provide amplespace for connections.

The rings are assembled in a jig with the holes in axial alignment; andafter brazing, a reamer is run through the holes in the metal rings toinsure as near perfect alignment of the edges 6 as possible.

Means within the ring assembly are provided for selectively closing thecircuit between each feed ring and one or the other of the associatedcontact rings. Arranged within the entire extent of the ring assembly isa ceramic shaft or stem 7, having wide grooves 8 spaced along itslength. The lower end is metallized and crowned with a nickel cap 9 towhich is brazed a circular steel armature plate 12.

Fitting in each of the grooves 8 is a molybdenum threesided split ringor resilient triadic shoe 13, shown alone in Fig. 4. The proportion ofparts is such as to seat each shoe in its groove so that there is noappreciable axial or transverse movement therein, and the rounded faces14 of the shoe lie in lightly resilient engagement with the inner edge 6of the associated feed ring 3f and the corresponding edge of the upper(or lower) contact ring 3c.

To prevent friction and Wear so far as practicable, the edges of theengaging parts are lightly chamfered and the surfaces polished.

It will be noted that for each feed ring and its associated contactrings, there are three separate points of resilient engagement with thetriadic shoe, so that while there is very little likelihood of animperfect electrical contact between one of the triadic shoe faces 14and its place of engagement wtih the inner edge 6 of a feed or contactring, there is substantially no chance whatever of such failure withthree such engagements in parallel with each feed and contact ring.

Each triadic shoe is continuously in resilient engagement at threeplaces with its associated feed ring; and with upward movement of thestem 7, three additional separate resilient sliding engagements are madewith the contact ring above, thus closing a circuit therethroughsimultaneously at three separate places. Downward movement of the stemopens the circuit previously made, and closes another one through threeseparate places of engagement with the lower contact ring of the group.

Thus with four groups of feed and contact rings, as

- shown in Fig. 1, four circuits are closed by upward movment of'thestern; and these are broken and four others closed by downward movement.

The upper end of the switch is hermetically closed by a metal top plate16 integrally united as by brazing tothe top-most ceramic ring; and ametal tube 17 provides rugged means for sealing off the envelope afterthe vacuumizing procedure has been completed.

Brazed-to the lower face of the bottom ceramic ring isa copper ring orannulus 18, having an external flange 19. This entire ring assembly oftop plate, tubulation andalterna-ted ceramic and metal rings, andflanged annulus is put together and then brazed in the furnace in oneoperation. The edges 6 of the central holes in the molybdenum rings arebrought into substantially perfect alignment by reaming, the entirecavity thoroughly cleaned, and the stem with attached armature and shoespushed into place.

Brazed to and axially ali ned with the ring assemblyis a steel housing21 containing the actuating elements of our switch. The housing has atransverse partition 22 brazed to and hermetically closing the housingnear its inner end, but leaving its free end outside the vacuumized partof the envelope. Mounted rigidly in the partition and'integrally unitedthereto is the electro-magnetic core 23, its inner end widened into thehead 24, just below and spaced from the armature 12. Between thepartition and the armature is the spiral spring 26, which normallypresses the armature and stem upwardly to close the upper series ofcontacts. The upper contacts are broken and the lower contacts closed,when the armature and stem are drawn down against the resistance of thespring; and this occurs when the coil 27 surrounding the core isenergized.

The coil is mounted on a base'plate 28, held on the lower end of thehousing 21 by a single screw 29 threaded into the end of the core. Leads31 for the windings on the coil pass through the plate in sealedbushings 32. Coils are-thus quickly removed and replaced, or exchangedfor others of different electrical values.

Before joining the housing '21 to the ring assembly we first braze anannular channel 33 to the rim of the housing along with a mountingflange 34; and then assemble the spring 26 around the head end of thecore. This unit is then placed within the-seat formed by the flangedring l$-i9, and brazed by heliarc, so that the heat of brazing islocalized, and excessive heat is not transmitted to other parts withinthe envelope.

- This heliarc brazing is done with a mixture of nitrogen and hydrogeninside the envelope at slightly above atmospheric pressure, so thatformation of oxides therein during the brazing is prevented, and thecleanliness of the parts is fully preserved. For this forming gasmixture, we use about 85% nitrogen and .15% hydrogen. Immediately afterthe heliarc brazing, the switch envelope .is ready for exhaustion andfinal bake-out heating.

The particular design shown is intended for direct current low voltageusage. Due to small size and high efiiciency, the actuating wattage iskept low and is predicated on the amount of dampening and internalfriction desired to make the switch withstand the required vibration andshock tests. it is obvious however that by expending the size of therings we can make a high voltage, heavy duty product using the samebasic technique to eliminate much of the costly hand work formerly required in producing vacuumized switches.

Our switch is particularly suitable for radio frequency service sinceinductance has been kept at a minimum, and no external mechanism isrequired for operation. No matter to what type of service our switch isto be applied, the coil assembly can be operated at ground potentialwithout danger offiashing over internally due to insuficientresistancetoground.

It will be obvious without specific illustration ordescription that ourinvention maybe embodied in a switch having any desired number of poles,either single or double throw, by a suitable number of ceramic ringsalternated with feed and contact rings, arranged 'as necessary to givethe desired single or double throw operation.

We claim:

1. In a vacuumized switch, a vacuumized envelope, a group of first andsecond and third conductive rings spaced axially inside the envelope andinsulated from each other by the wall of the envelope, a unitaryconductive shoe having a plurality of integrally connected slide facesslidably engaging the inner edge of the second conductive ring, andmeans for moving the shoe to slidably engage selectively the first orthird conductive ring while maintaining its engagement with the secondring.

2. The combination of claim 1 in which the means for moving the shoe inone direction is a spring within the vacuumized ring assembly and formoving the shoe in the opposite direction is a magnetic coil outside thering assembly.

3. A vacuumized switch comprising a plurality of metallized ceramicrings, conductive feed and contact rings interposed between the ceramicrings and brazed thereto to unite all the rings in an hermetically tightassembly, each feed ring spaced between two contact rings, an end platestructure hermetically closing each opposite end of the ring assembly, anononducting stem within thering assembly, a conductive shoe having aplurality of slide faces resiliently engaging the inner edge of eachfeed ring and arranged on the stem, and means for moving the stemselectively to engage each shoe with the inner edge of the contact ringon eitherside of the associated feed ring while maintaining itsengagement with the feed ring.

4. A vacuumized switch in accordance with claim 3 in which each or" theconductive feed and contact'rings has an integral tab extending throughthe wall of the ring assembly to constitute a terminal outside the ringassembly.

5. The combination of claim 4 in which an armature plate is fixed on oneend of the stem and within the hermetically tight ring assembly and aspring is arranged to move the armature plate and stem in one direction,and outside the ring assembly 'a magnetic coil is arranged to move thearmature plate and stem in the opposite direction.

6. A multiple pole vacuum switch comprising an as sembly of alternaterings of metallized ceramic and metal brazed together, each of the metalrings having an externally extending terminal lug'and a central aperturein axial alignment with the apertures of the other metal rings, a metalplate brazed to and closing one end of the ring assembly, a housinghaving an integrally unitedpartition extending thereacross and brazed toand closing the opposite end of the ring assembly, a non-conducting stemaxially arranged within the ring assembly, a conductive shoe mounted onthe stem and in continuous sliding engagement with one of said metalrings, and means arranged on both sides of the partition in said housingfor moving the stern selectively to engage and disengage the shoe withthe metal ring on either side of the ring continuously engaged by theshoe.

7. In a multi-polar switch a plurality of parallel conductive ringsinsulated from each other and having apertures axially aligned therein,a dielectric stem extending axially through the aligned apertures, and aplurality .of conductive shoes comprising axially spaced resilienttriadic rings fixed on the stem for axial movement therewith and eachshoe in continuous engagement with oneassociated ring and indiscontinuous and selective sliding engagement with other associatedrings.

8. In a multi-polar switch, a cylindrical dielectricstem having aplurality of annular grooves spaced therealong, and asplit triadic ringdisposed in each groove and constituting a contact shoe.

(References on following page) References Cited in the file of thispatent 2,633,485 UNITED STATES PATENTS 21649890 285,778 Adams Oct. 2,1883 453,484 Jewell June 2, 1891 5 1,486,386 Laing Mar. 11, 1924 206,8412,156,974 D0811 May 2, 1939 594,282

Patnode Mar. 31, 1953 Johnson June 2, 1953 FOREIGN PATENTS Great BritainMay 1, 1924 Germany Mar. 14, 1934

